Re: [PATCH 0/4] repack: various corner cases for cruft-less MIDXs

On Tue, Sep 29, 2026 at 08:28:34PM -0500, Taylor Blau wrote:

This patch series fixes a few bugs I spotted while investigating the
cruft-less MIDX feature.

The bugs addressed are found in various corner cases, and, when
triggered, may result in a MIDX being written whose objects are not
closed under reachability. When this happens while the caller is trying
to write reachability bitmaps, bitmap generation may fail if one or more
selected commits are descendants of the open portion of the MIDX.

I think all of these are making things strictly better, but I did find a
few spots where the fixes might be incomplete. I'm not sure if that
argues for a re-roll or for punting those to future work. ;)

I agree with Stolee that an oidset is perhaps a better data structure
for storing the extra roots (which are in a kind-of random order anyway,
since we're pulling them in pack order from various packs). But it also
probably doesn't make that big a difference in practice (we'll skip
duplicates during the traversal, and you probably don't have that many
duplicate objects in a repo in the first place).

-Peff